Method and apparatus for forming flexible corrugated members

ABSTRACT

A method and apparatus for converting smooth walled tubular members into corrugated flexible members. The invention contemplates stamping grooves of progressively increasing depth into the outer walls of the smooth tube and thereafter compressing the thus corrugated member while preventing deformation and expansion in the radial direction to thereby define a flexible tube characterized by a helically corrugated wall.

[75] Inventor:

United States Charvet atet 11 1 [4 1 Nov. 11,1975

[ METHOD AND APPARATUS FOR FORMING FLEXIBLE CORRUGATED MEMBERS Joseph Charvet, Bessancourt (Val dOise), France [73] Assignee: Societe Francaise de Tuyaux Metalliques/Flexibles, Paris, France [22] Filed: Mar. 30, 1971 [21] Appl. No.: 129,357

Related U.S. Application Data [63] Continuation-impart of Ser. No. 738,215, June 19,

1968, abandoned.

[30] Foreign Application Priority Data Picece et a1. 72/77 2,023,417 12/1935 Guarnaschelli ..72/77 FOREIGN PATENTS OR APPLICATIONS 881,154 11/1961 United Kingdom 72/77 561,294 10/1957 Belgium 72/115 151,270 11/1937 Austria 72/77 Primary E.\'aminerRichard J. Herbst ABSTRACT A method and apparatus for converting smooth Walled tubular members into corrugated flexible members. The invention contemplates stamping grooves of progressively increasing depth into the outer walls of the smooth tube and thereafter compressing the thus corrugated member while preventing deformation and expansion in the radial direction to thereby define a flexible tube characterized by a helically corrugated wall.

12 Claims, 3 Drawing Figures l I? "[IILQ'II M IL'T'IIILII? a, A 2. /2 :II' e115,; /3

US. Patent N0v.11, 1975 Sheet2of2 3,918,285

METHOD AND APPARATUSFOR FORMING FLEXIBLE CORRUGATED MEMBERS CROSS REFERENCE TO RELATED APPLICATIONS This invention is a continuation-in-part of application Ser. No. 738,215, now abandoned, which was filed June 19, 1968 claiming priority upon parent French application Ser. No. 111,251 of June 21, 1967.

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to the conversion of smooth walled, relatively rigid tubular members into corrugated, bendable members. More specifically, the present invention is directed to apparatus for the formation of helical corrugations in the outer wall of a smooth tubular member. Accordingly, the general objects of the present invention are to provide novel and improved methods and apparatus of such character.

2. Description of the Prior Art Several methods are known in the prior art which enable smooth walled tubular members to be transformed into corrugated members characterized by flexibility. One of the more common prior art methods comprises the transverse deformation of a cylindrical tube by forcing the wall thereof inwardly to the full depth of the desired finished corrugations and thereafter applying longitudinal pressure to reduce the pitch of the corrugations. In this prior art method, as well as in other known techniques, nomeans are provided to limit the expansion in the radial direction of the folds formed in the tube wall. Similarly, prior art techniques did not provide means to insure uniform distances between the folds or corrugations while the longitudinal pressure required toreduce the pitch of the corrugations was applied. A further disadvantage of the prior art resided in the absence of means for uniformly distributing the applied longitudinal pressure amongst the successive folds of the corrugation. Finally, prior art methods and apparatus for forming flexible corrugated tubes did not permit continuous operation.

SUMMARY OF INVENTION The present invention overcomes the foregoing and numerous other disadvantages of the prior art by providing a novel method and apparatus for the manufacture of flexible corrugated tubes having helicoidal turns. In accordance with the invention, a hollow cylinder entirely enclosed by an external die is deformed without internal support. The external die defines a profile calculated so as to obtain regular progressivity of the deformation in order to insure permanent contact points with relation to the tubular member being deformed when relative movement of rotation and translation in the axial direction are produced between the cylinder and the die.

Apparatus for practicing the method of the present invention comprises at least two dies or, alternatively, a die having at least two portions. Thefirst die or first die portion effects the stamping of thesmooth walled tubular member to, a progressively increasing depthin the centriperal radial direction so as to provide at least two helicoidalconvolutions which are concave in relation to the outer surface of the original tube. The second die or die portion effects thecompression of the opposite flanks of the convex conv olutio ns, and p articularlyin the space between two successive concave con volutions, resulting from the stamping step. The compression of the tubular member will preferably be progressive. In accordance with a preferred embodiment of the invention, the die or dies have the external form of a nut. Also, depending on the depth of the convolution and on the desired progressivity, the screw thread defined by the dies may comprise one or more convolutions.

The second die or die portion, as noted, performs a compression operation which progressively folds the wave or thread created by the stamping of the first die portion. The second die will typically have a constant bore diameter equal to the bore diameter at the outlet of the first die or die portion whereby there will be no further radial stamping action as the member proceeds from the first die into the second die. The second or compression die will preferably be characterized by a regularly decreasing pitch which effects the compression of the flanks of the convolution.

The present invention may also comprise a third die or die portion which verifies or finishes the contour of the finished product. When included, the third die or die portion will comprise a nut having an internal thread of constant pitch and of constant bore diameter.

BRIEF DESCRIPTION OF THE DRAWING The present invention may be better understood and its numerous objects and advantages will become apparent to those skilled in the art by reference to the accompanying drawing wherein like reference numerals refer to like elements in the several figures and in which:

FIG. 1 is a cross-sectional view of a first embodiment of the invention; the embodiment of FIG. 1 comprising three die portions;

FIG. 2 is a cross-sectional view of a second embodiment of the invention wherein two die portions are utilized; and

FIG. 3 is a cross-sectional view of a third embodiment of the invention which employs three die portions formed in'two die members.

- DESCRIPTION OF THE PREFERRED EMBODIMENTS With reference now to FIG. 1, the disclosed embodiment is shown as comprising three assembled dies. Each of these dies is characterized by having the external shape of a nut; the three dies being respectively indicated by reference numerals 1, 2 and 3. In operation, the dies 1, 2 and 3 and the tubular workpiece 4 are rotated relative to each other about axis XX. The requisite rotation is achieved through the use of any suitable device and thus the rotating means has not been shown in the interest of facilitating understanding of the invention. It is to be understood that, during rotation, the dies 1, 2 and 3 are restrained from translational motion in order to effect advancement of the workpiece in the downward direction as shown in FIG.

1. The first or uppermost die 1 is the stamping die and has an internal screw thread of constant pitch. However, the bore'diameter of die 1 decreases regularly proceeding from point 5 serially to points 6, 7 and 8.

The internal thread of die 2, which is the compres- "sion die, has a constant bore diameter defined by die sections 9 and 10. However, as can be seen through comparison of sections II and 12 of die 2, the bottom diameter of the thread increases in the direction of movement of the workpiece through the compression die.

The third or finishing die 3 comprises a nut having an internal thread with constant diameter and pitch as illustrated.

In operation, the dies are assembled and restrained to prevent translational movement along the axis XX. Thereafter, either the dies or the workpiece, or both, are rotated about axis XX so as to cause the workpiece 4 to advance through the dies. This technique is, of course, different from the prior art and makes it possible to continuously machine tubes of much greater length than previously possible. That is, the present invention does not require internal support of the tubular member and thus may be practiced starting with a strip which is welded into tubular shape before it enters the dies; it thus being possible to operate continuously with rotation of the workpiece affecting its advance in stationary dies.

As will be obvious to those skilled in the art, the die 1 produces helicoidal waves of progressively increasing depth and of constant pitch in the outer wall of the tubular member 4. The die 2 effects the compression of the helicoidal waves by acting on the flanks thereof to produce a progressively decreasing pitch.

As noted above, because of the presence of die 2, the third or finishing die 3 has little effect on the finished product since die 3 does not act either on the pitch or the depth of the thread formed in the workpiece 4.

It will be observed that the screw threads of the three dies should constitute a continuing, non-interrupted thread. That is, preferably the end of a thread in a preceding die should coincide with the beginning of the thread on the next succeeding die in the direction of workpiece advancement. In order to accomplish the foregoing, it will be advantageous for any discontinuity of the curve defined by the threads to be attenuated by special machining at the abutment points between the dies. It will also be observed that, when assembled, the two or three dies do not necessarily abut against one another along plain surfaces perpendicular to the axis of rotation.

With reference now to FIG. 2, it is to be noted that the disclosed embodiment comprises only the dies 1 and 3; the number of threads of die 3 being increased when compared to the embodiment of FIG. 1. While the compression die 2 has been omitted from the embodiment of FIG. 2, the apparatus achieves an equivalent result when compared to the embodiment of FIG. 1 by imparting a rotation about the common axis to die 3. Such a rotation causes an oblateness which results in a reduction of the pitch.

Referring to FIG. 3, a third embodiment is disclosed wherein the dies 1 and 2 have been combined in a single nut 12. Nut or die 12 is comprised of portions 13 and 14 which correspond respectively to dies 1 and 2 of the embodiment of FIG. 1. The third or finishing die is shown in FIG. 3. It is, however, to be understood that the finishing die may be eliminated as discussed above.

It is to be emphasized that, depending on the materials to be machined, the present invention may be practiced by utilizing only the first and third dies or portions thereof as shown in FIG. 2. When the second or compression die is omitted, the third or finishing die performs the compression function. As noted above, this is accomplished by rotation of the third die about the axis XX' to provide an angular displacement relative to the position where the thread of the finishing die would form a continuation of the thread of the first or stamping die. In cases where the second die is omitted the compression will be severe and it is usually desirable to employ the second die in the interest of obtaining a more progressive compression.

In application, the present invention may be employed with workpieces of any deformable metallic or synthetic material. The steps of stamping and/or compression, particularly when the workpiece is comprised of a thermoplastic synthetic material, may be per formed with the aid of suitable heating devices for the purpose of bringing the tubular member to the proper working temperature.

As will now be obvious to those skilled in the art, the present invention may replace previous equipment of similar character in existing machines. When compared to the prior art, which employs internal support shafts with their attendant disadvantages, the present invention eliminates the danger of twisting and the necessity of practicing the invention with a seamless tube or a redrawn welded tube. Also, since the dies of the present invention preferably have the external shape ofa nut or nuts, assembly, disassembly and use of the present invention is considerably easier than that of previous tools. Similarly, fabrication of the tool is facilitated in accordance with the present invention.

As noted above, the present invention also has the added advantage of being capable of use to corrugate welded tubes. The present invention may also be practiced using strip which is continuously welded in order to form the workpiece. The latter advantage, in turn, permits the present invention to be practiced continuously thus constituting a substantial advantage when compared to the prior art.

Accordingly, while preferred embodiments have been shown and described, various modifications and substitutions may be made thereto without departing from the spirit and scope of the present invention. Thus, for example, the invention is not limited to the production of a sinusoidal corrugation or to the production of folds or corrugations which are nearly in contact with one another. Thus, it is to be understood that the present invention has been described by way of illustration and not limitation.

What is claimed is:

l. A die for providing a tube with a continuous helical corrugation comprising:

at least two rigid non-interrupted continuous portions, each of said portions having a length dimension defining a bore extending therethrough, said portions having their bores aligned coaxially, the first of said portions having its bore machined to form a continuous rigid grooveforming helical thread with convolutions having a constant pitch and an inner diameter which decreases progressively in the direction of the second portion, the second of said portions having its bore machined to form a continuous groove-forming helical thread having a substantially constant inner diameter and a pitch which decreases progressively towards the end of the bore disposed away from said first portion, said helical thread of said second portion forming a continuation of the helical thread of said first portion.

2. A die as set forth in claim 1 further comprising a third portion having a length dimension defining a bore extending therethrough, said bore being coaxial with the bores of both of said other portions, said third portion having its bore machined to form a continuous rigid groove-forming helical thread having a constant pitch and a constant inner diameter, said helical thread of said third portion forming a continuation of the helical thread of said second portion.

3. Apparatus as set forth in claim 2 in which the dies are assembled together by plane surfaces which are oblique relatively to their common axis.

4. A die as set forth in claim 1 having the general external form of a nut.

5. A die for providing a tube with a continuous helical corrugation comprising:

at least two rigid non-interrupted continuous portions, each of said portions having a length dimension defining a bore extending therethrough, said portions having their bores aligned coaxially, the first of said portions having its bore machined to form a continuous rigid groove-forming helical thread with convolutions having a constant pitch and an inner diameter which decreases progressively in the direction of the second portion, the second of said portions having its bore machined to form a continuous groove-forming helical thread having a substantially constant inner diameter and a constant pitch, said portions being assembled together by giving to the second of said portions, by rotation about the common axis, an angular displacement relatively to the position in which the helical thread of said second portion would form a continuation of the helical thread of said first portion.

6. A die as set forth in claim 5 having the general external form of a nut.

7. Apparatus for providing a tube with a continuous helical corrugation comprising:

at least two rigid non-interrupted continuous dies,

each of said dies having a length dimension defining a bore extending therethrough, said dies being assembled with their bores aligned coaxially, the first of said dies having its bore machined to form a continuous rigid groove-forming helical thread with convolutions having a constant pitch and an inner diameter which decreases progressively in the direction of the second die, the second of said dies having its bore machined to form a continuous groove-forming helical thread having a substantially constant inner diameter and a pitch which decreases progressively towards the end of the bore disposed away from said first die, said helical thread of said second die forming a continuation of the helical thread of said first die.

8. The apparatus as set forth in claim 7 further comprising a third die having a length dimension defining a bore extending therethrough, said bore being coaxial with the bores of said first and second dies, said third die having its bore machined to form a continuous rigid groove-forming helical thread having a constant pitch and a constant inner diameter, said helical thread of said third die forming a continuation-of the helical thread of said second die.

9. Apparatus as set forth in claim 7 in which the dies have the general external form of a nut.

10. Apparatus for providing a seamless or seamwelded tube with a continuous helical corrugation comprising:

at least two rigid non-interrupted continuous dies,

each of said dies having a length dimension defining a bore extending therethrough, said dies being assembled with their bores aligned coaxially, the first of said dies having its bore machined to form a continuous rigid groove-forming helical thread with convolutions having a constant pitch and an inner diameter which decreases progressively in the direction of the second die, the second of said dies having its bore machined to form a continuous groove-forming helical thread having a substantially constant inner diameter and a constant pitch, said dies being assembled together by giving to the second of said dies, by rotation about the common axis, an angular displacement relative to the position in which the helical thread of said second die would form a continuation of the helical thread of said first die.

11. Apparatus as set forth in claim 10 in which the dies have the general external form of a nut.

12. Apparatus as set forth in claim 10 in which the dies are assembled together by plane surfaces which are oblique relatively to their common axis. 

1. A die for providing a tube with a continuous helical corrugation comprising: at least two rigid non-interrupted continuous portions, each of said portions having a length dimension defining a bore extending therethrough, said portions having their bores aligned coaxially, the first of said portions having its bore machined to form a continuous rigid groove-forming helical thread with convolutions having a constant pitch and an inner diameter which decreases progressively in the direction of the second portion, the second of said portions having its bore machined to form a continuous groove-forming helical thread having a substantially constant inner diameter and a pitch which decreases progressively towards the end of the bore disposed away from said first portion, said helical thread of said second portion forming a continuation of the helical thread of said first portion.
 2. A die as set forth in claim 1 further comprising a third portion having a length dimension defining a bore extending therethrough, said bore being coaxial with the bores of both of said other portions, said third portion having its bore machined to form a continuous rigid groove-forming helical thread having a constant pitch and a constant inner diameter, said helical thread of said third portion forming a continuation of the helical thread of said second portion.
 3. Apparatus as set forth in claim 2 in which the dies are assembled together by plane surfaces which are oblique relatively to their common axis.
 4. A die as set forth in claim 1 having the general external form of a nut.
 5. A die for providing a tube with a continuous helical corrugation comprising: at least two rigid non-interrupted continuous portions, each of said portions having a length dimension defining a bore extending therethrough, said portions having their bores aligned coaxially, the first of said portions having its bore machined to form a continuous rigid groove-forming helical thread with convolutions having a constant pitch and an inner diameter which decreases progressively in the direction of the second portion, the second of said portions having its bore machined to form a continuous groove-forming helical thread having a substantially constant inner diameter and a constant pitch, said portions being assembled together by giving to the second of said portions, by rotation about the common axis, an angular displacement relatively to the position in which the helical thread of said second portion would form a continuation of the helical thread of said first portion.
 6. A die as set forth in claim 5 having the general external form of a nut.
 7. Apparatus for providing a tube wIth a continuous helical corrugation comprising: at least two rigid non-interrupted continuous dies, each of said dies having a length dimension defining a bore extending therethrough, said dies being assembled with their bores aligned coaxially, the first of said dies having its bore machined to form a continuous rigid groove-forming helical thread with convolutions having a constant pitch and an inner diameter which decreases progressively in the direction of the second die, the second of said dies having its bore machined to form a continuous groove-forming helical thread having a substantially constant inner diameter and a pitch which decreases progressively towards the end of the bore disposed away from said first die, said helical thread of said second die forming a continuation of the helical thread of said first die.
 8. The apparatus as set forth in claim 7 further comprising a third die having a length dimension defining a bore extending therethrough, said bore being coaxial with the bores of said first and second dies, said third die having its bore machined to form a continuous rigid groove-forming helical thread having a constant pitch and a constant inner diameter, said helical thread of said third die forming a continuation of the helical thread of said second die.
 9. Apparatus as set forth in claim 7 in which the dies have the general external form of a nut.
 10. Apparatus for providing a seamless or seam-welded tube with a continuous helical corrugation comprising: at least two rigid non-interrupted continuous dies, each of said dies having a length dimension defining a bore extending therethrough, said dies being assembled with their bores aligned coaxially, the first of said dies having its bore machined to form a continuous rigid groove-forming helical thread with convolutions having a constant pitch and an inner diameter which decreases progressively in the direction of the second die, the second of said dies having its bore machined to form a continuous groove-forming helical thread having a substantially constant inner diameter and a constant pitch, said dies being assembled together by giving to the second of said dies, by rotation about the common axis, an angular displacement relative to the position in which the helical thread of said second die would form a continuation of the helical thread of said first die.
 11. Apparatus as set forth in claim 10 in which the dies have the general external form of a nut.
 12. Apparatus as set forth in claim 10 in which the dies are assembled together by plane surfaces which are oblique relatively to their common axis. 